Step 1: Jailbreak your 4.3.1 iDevice using Sn0wbreeze 2.5.1, step by step guide for which can be found here. While jailbreaking, make sure you enable the option “Enable Animated Logo Capability” found under Expert Mode->General, as shown in the screenshot below.

Step 2: Once your iPhone, iPad or iPod touch has been jailbroken, start Cydia and install “Apple Boot Logo” (aka Animate), and you’re well on your way to some animated goodness.

Now you need some themes, which can be found by searching Cydia for ‘BootLogo’ and install whichever themes take your fancy.

Once all that is done it’s just a matter of firing up Settings.app and choosing which theme you want to use from the new BootLogo menu.